1. Field of the Invention
The present invention relates to a semiconductor processing apparatus and method and, more particularly, to a film formation technique. A semiconductor process indicates various processes executed to manufacture, on a target substrate, a structure including a semiconductor device, and interconnections and electrodes connected to the semiconductor device by forming semiconductor layers, insulating layers, and conductive layers in a predetermined pattern on the target substrate such as a semiconductor wafer or a glass substrate for a liquid crystal display (LCD) or flat panel display (FPD).
2. Description of the Related Art
In manufacturing a semiconductor device, a processing apparatus is used to execute various processes such as oxidation, diffusion, CVD, and annealing for a target substrate such as a semiconductor wafer. Jpn. Pat. Appln. KOKAI Publication No. 2003-218098 discloses an apparatus of this type to execute a film formation process. This processing apparatus has a process chamber to accommodate a target substrate such as a semiconductor wafer and process it at a predetermined temperature and pressure in a predetermined gas atmosphere. A process gas supply system and vacuum exhaust system are connected to the process chamber. The vacuum exhaust system has an opening variable valve. A ballast control unit to control the pressure by introducing an inactive gas is arranged on the downstream side of the opening variable valve. In the film formation process, the opening variable valve is fully opened, and the introduction flow rate of the inactive gas is controlled by the ballast control unit, thereby controlling the pressure in the film formation process.
According to this processing apparatus, deposition of a reaction by-product on the opening variable valve can be suppressed to some extent by fully opening the opening variable valve during the film formation process. Since the maintenance period of the apparatus can be prolonged, the apparatus down time in removing the reaction by-product can be reduced to some degree. However, the present inventors have found that deposition of a reaction by-product on the opening variable valve poses a problem even in this processing apparatus depending on the process contents, as will be described later.